A massive proliferation of Karenia mikimotoi, a highly toxic microalgae, has caused an ecological collapse in southern Australia, affecting over 4,500 km² of coastal waters and leading to the death of more than 15,000 marine animals from 450 different species.
Ecologist Scott Bennett describes it in a statement as the transformation of entire ecosystems into true “underwater deserts”.
Early signs: yellow foam and respiratory symptoms
The phenomenon was detected in March, when surfers reported dry cough, sore throat, and blurred vision. Shortly after, a yellowish foam appeared in the waves and dead animals washed up on the beaches.
Researchers identified Karenia mikimotoi as the culprit: a microalgae that, in high concentrations, damages gills, blocks sunlight, and causes hypoxia, suffocating marine life.
The Great Southern Reef, in critical condition due to the toxic microalgae
The situation is particularly serious in the Great Southern Reef, home to exceptional biodiversity, with 70% of endemic species. “100% of the razor clams were dead and rotting on the seabed,” Bennett reported after touring the area. The loss of these species implies an irreversible extinction.
The disaster not only affects the environment: it has also hit the fishing industry hard, valued at 480 million Australian dollars.
Fishers claim to not have caught a single squid since April and warn that a third of state waters are devoid of life. The crisis extends to processors, distributors, and restaurants, leaving hundreds of workers in uncertainty.
Climatic causes: nutrients, upwellings, and extreme heat
Scientists point out that this proliferation was driven by a series of climatic factors:
- Floods in 2022, which carried nutrients into the ocean
- Upwelling of cold nutrient-rich waters
- A marine heatwave in September 2024, which raised sea temperature 2.5°C above average
This combination of conditions created the perfect environment for the explosive growth of the microalgae.
Official response: limited funds and lack of recognition
South Australian Prime Minister Peter Malinauskas acknowledged the severity of the event: “It’s a natural disaster, but unlike anything we’ve ever known.” Although 28 million Australian dollars have been allocated for cleanup and assistance, it has not been formally declared a natural disaster, preventing the release of additional funds.
A symptom of ongoing climate change
Scott Bennett warns that this event should not be seen as isolated: “It is part of the climate impact affecting all of Australia.” Although marine ecosystems have resilience, it is essential to protect strategic habitats such as:
- Seaweed forests
- Submarine meadows
- Oyster reefs
These environments help filter nutrients, stabilize the ecosystem, and mitigate future collapses.
A global alert from the depths of the ocean
The tragedy caused by Karenia mikimotoi is a clear warning of the oceans’ fragility in the face of climate change and pollution.
Recovery will require coordinated actions, environmental education, and robust conservation policies to prevent these “underwater deserts” from becoming the new normal.
